Transient Magnetization in Practical Composite Superconductors

摘要

This paper presents detailed magnetization measurements as well as analysis on typical cryostable NbTi composite conductors (1-mm diameter and Cu/SC ratio of 6:5) with filaments nonuniformly distributed in both circular and rectangular cross sections (aspect ratio approx. 2:1). As a result of the excellent agreement between the measurements and a previously reported transformer model, both transient magnetization and losses incurred in each sample can be described by functions of a unique time constant tau sub 0 which depends strongly on the shape of the cross section. Other prominent features of the measurement results such as the deduction of values of J/sub c/ and matrix resistivity are demonstrated. In an exponentially decaying field from 2T to 0, J/sub c/ is 4.5 x 10 exp 9 A/m exp 2 at 1.5T, and the average matrix resistivity is 2.73 x 10 exp -10 omega -m. Saturation effects were also observed for field decaying time constant tau comparable with tau sub 0 . (ERA citation 05:002205)